Real sci-fi space ships coming at last? NASA tests nuclear engine

NASA has conducted tests of a nuclear reactor intended to generate electricity in space for the first time since 1965, offering hope that humanity may now belatedly get serious about building proper, powerful spaceships of the sort long envisaged in science fiction.

The space agency has just announced the tests, conducted by engineers from NASA's Goddard centre in conjunction with Department of Energy boffins from the Los Alamos national lab. The effort made use of an experimental reactor named "Flattop" and was inauspiciously dubbed Demonstration Using Flattop Fissions (DUFF).

According to the Goddard announcement:

On September 13, the research team demonstrated the first use of a heat pipe to cool a small nuclear reactor and the first use of a Stirling engine to convert the reactor heat into electricity.

A heat pipe is a sealed tube with an internal fluid that can efficiently transfer heat produced by a reactor with no moving parts. Heat pipe technology was invented at Los Alamos in 1963 and is used widely by NASA for aerospace applications. A Stirling engine is a relatively simple closed-loop engine that converts heat energy into electrical power using a pressurized gas to move a piston within a magnetic field. Using the two devices in tandem allowed for creation of a simple, reliable electric power supply that could be adopted for space applications.

DUFF is the first demonstration of a space nuclear reactor system to produce electricity in the United States since 1965. It confirms the basic nuclear reactor physics and heat transfer for a simple, reliable space power system.

Long ago in the 1940s and '50s it was already quite apparent to technically knowledgeable folk that chemically fuelled rockets would never offer enough power for routine travel into orbit or manned interplanetary voyages. Nor can conventional electricity sources such as fuel cells or solar power produce enough juice for any but the most limited spacegoing operations.

As a result, the technically accurate science fiction authors of the day assumed that more powerful nuclear technology would naturally be adopted, offering rockets that could get into space without throwing most of themselves away and manned ships capable of travelling about the solar system on timescales shorter than years or decades.

As everyone knows, it never happened. The only human beings who have ever travelled beyond Earth orbit are the Apollo moon astronauts of long ago. Robots, generally power-starved, have done some limited exploration further afield by coasting through space for years on end to reach their destinations. There has been very little real advancement for decades: the human race and its activities remain firmly chained to planet Earth.

The US didn't completely give up on nuclear technology for space use after 1965: the NERVA programme, in which a nuclear reactor was intended to provide rocket propulsion as opposed to electric power, carried on until 1972 before cancellation. After that, however, US nuclear technology for space was limited to comparatively feeble radioisotope generators which rely on their fuel to decay on its own rather than stimulating a chain reaction.

A few small nuclear reactors did go into space aboard Soviet spy satellites, and Russia still maintains vague aspirations towards a proper nuclear-powered spaceship, but until today very little real-world hardware has appeared.

But perhaps DUFF is a signpost to a brighter future? It would be nice to think so.

"The nuclear characteristics and thermal power level of the experiment are remarkably similar to our space reactor flight concept," says Los Alamos engineer David Poston.

Perhaps we're finally looking at a hefty space reactor, able to power sophisticated plasma rockets and carry a crew to Mars in just a month?

Not so much, sadly.

"A flight system might use several modules to produce approximately one kilowatt of electricity," says Marc Gibson of NASA Glenn. That's not even enough to heat up a kettle, though it is ten times as much as the famous Mars rover Curiosity can generate with its radioisotope battery.